Lubricant



Patented Mar. 13, 1945 LUBRICANT William B.- Ross, Evanston, William J.Backofl, Elmhurst, and Norman D. Williams, Chicago, Ill., assignors toThe Pure Oil Company. Chicago, 111., a corporation of Ohio No Drawing.Application July 16, 1942,

- Serial No. 451,218

2 Claims.

This invention relates to the problem of inhibiting bearingcorrosion andoil deterioration in internal combustion engines, and is moreparticularly directed to the use of' a particular'class of compounds asinhibitors in conjunction with mineral lubricating oils for thelubrication of moving parts of an internalcombustion engine.

In recent years alloys such as cadmium-silver, cadmium-silver-copper,cadmium-nickel-copper and copper-lead have been substituted -for babbittas hearing metals. Although these alloys have mechanical advantages overBabbitt metal, under modern operating conditions they appear to promoteoxidation of the lubricating oil, resulting in varnish and sludgeformation with attendant. valve and ring sticking. The use of thesebearings also is attended with high bearing losses, probably due tocorrosion by acids formed by the oxidation of the oil.

Because of the rapid rate of deterioration of lubricating oils and therapid rate of corrosion of bearings in modern internal combustionengines of the automotive type much research has been conducted on theproblem of inhibiting deterioration and corrosion, and a large number ofcompounds have been developed which-are effective to some extentiii-inhibiting deterioration of the oil and corrosion of the bearings.

We have discovered a class of compounds which exhibit exceptionalability to inhibitdeterioration of "motor oil and corrosion of bearingswhen used in relatively small quantities.

An object of this invention is to inhibit deterioration of motor oilandto inhibit corrosion of bearings in internal combustion engines? Afurther object of the invention is to provide a composition of-mattercapable of lubricating means for contacting the bearings and othermoving parts of the internal combustion engine with an ester or salt ofa thio-carbamic acid, in

the presence of mineral lubricating oil. Although the salt or ester ofthe thio-carbamic acid may be injected into the engine independently ofthe lubricating oil, we prefer to mix thematerial in small quantitieswith the lubricating oil prior to adding it to the engine. Although itis not essential that the salt or ester be soluble in the oil, we preferto use a soluble material in order to insure against separation of themate-.- rial from the on during use. The invention, however,contemplates the use of salts or esters which are not soluble but whichare high] dispersed in and held in suspension in the oi; As

' examples of compounds which are suitable may be mentioned alkyl, aryland aralkyl esters of mono-thio-carbamic, di thio carbamic, and thiophospho carbamic acids in which hydrogen in 7 stituted by aryl, alkyl,

internal combustion engines containing bearterioration during use.

Further objects of this invention will appear from the followingdescription.

In accordance with our invention we provide or aralkyl radicals.Specific compounds which may be mentioned as examples are benzyl dibutyldithio carbamate and the butyl ester of dibutyl dithiocarbamic acid.

As examples of salts may be mentioned the alkaline earth metal saltsincluding barium, calcium, strontium and magnesium of mono-thio-car-i.

bamic, di-thio-carbamic and thio-phospho carbamic acids.

Although the aforesaid esters and salts are ef.-,

fectivewhen added to lubricating oil in amourit s as low as 5% by weightand amounts greater g y weight, the preferable rangeis from- .5 to 5% byweight based on the mineral oil.

In order to demonstrate the .emcacy of the thio carbamic acid esters andsalts as inhibitors against bearing corrosion and motor oildeterioration, Underwood tests were made using various amounts of benzyldibutyl'uithio carbamate and butyl ester of dibutyldithio car- -bamateacid in mineral lubricating oil and the bearing materials and theirapplications, by

A. F. Underwood, Journal of Society of Automotive Engineers, volume 43,pages 385-392, September 1938.

A catalyst consisting of .12% iron naphthenate by weight was added tothe oil in each run. This percentage is equivalent to .01% iron as ironoxide. The use of an iron catalyst is standard practice for theUnderwood test.

Additive #2=butyl ester dibutyl dithio carbamic acid. Additive #1=benzyldibutyl dithio carbamate.

sludge were obtained in the following manner:

Naphtha insoluvle (insoluble sludge) Three grams of the oil is mixed inan Erlenmeyer fiask with 100 cc. of A. S. T. M. precipitation naphtha,of the type specified in A. S. T. M. Method D91-35. The oil and naphthaare thoroughly mixed and allowed to stand for three hours. The insolublematter is then filtered through a tared Gooch porcelain crucible,previously prepared with an asbestos pad 1" thick and dried in an ovenat 300 F. for 30 minutes. The insoluble residue is washed with 100 cc.A. S. T. M. naphtha and'dried in an oven at 300 F. for thirty minutes,cooled and weighed. The increase in weight is naphtha insoluble.

chloroform soluble The chloroform soluble is extracted'from the driedand weighed naphtha insoluble residueby pouring successive portions ofchloroform through the filter pad using light suction. 100 cc. ofchloroform is generally suflicient but the 'extraction should becontinued until the filtrate is colorless. .,(With heavy naphthainsoluble residues the chloroform is allowed to stand in the cruciblewithout suction for a few minutes before each portion of the chloroformis drawn through the crucible.)

Theresidue is then dried in an oven at 300 F. for 30 minutes, cooled andweighed. The loss in weight is chloroform soluble. The solubility inchloroform of the residue from the naphtha insoluble determination isaffected by the time and temperature of drying. For this reason, inorder to secure check results in the chloroform soluble" determination,the drying time and temperature, especially in the naphtha insolubledetermination, should be carefully controlled.

It usually happens that in the Underwood test there is no particulardifliculty in filtering, re-

gardless of whether the oils contain detergents 'or not. However, whenthese methods are applied to used crankcase oils it sometimes happensthat oils which contain detergents will not give a clear filtrate. Underthese conditions, the filtrate is refiltered through a second Goochfilter and Table Per cent by wt. additive .0 3 l 0. 5 Additive No None#1 #1 #1 #1 Hours run 1 l0 l0 10 CuPb loss .0198 0176 0318 0380 AgCdloss .0041 0030 .0045 .0071 Neutralization No 0. 69 0. 61 1. 40 1. 63Per cent naph. insol. 0. 36 0. 42 0. 45 0. 61 Per cent CHCla sol-.. 2.88 0. 21 0. 22 0. 29 0. 29 Per cent sol. sludge 8. 35 0. 23 0. 0. 87 1.49 Per cent S. in blend from additive. 0 l. 085 661 217 1085 000M I S.on

aavns o the deposits from both crucibles added in reporting naphthainsoluble (and chloroform soluble).

Propane insoluble (soluble sludge) The filtrate from the naphthainsoluble is concentrated to 20 cc. by evaporation and is transferredquantitatively to the extraction apparatus described in Industrial 8;Engineering Chemistry April 15, 1939, page 183. The remaining naphtha isnow completely removed from the oil sample by evaporation on a steambath. The propane extraction is carried out as directed in theabovementioned article. The propane insoluble material remaining iscalculated in percentage and reported as soluble sludge. I

The data 'in the tables show that benzyl d butyl di thio carbamate waseflective in amount:

' of from .5 to 5% in cutting downbearing lossir both copper lead andsilver cadmium bearing: and. that it was effective in these percentagesir improving the neutralization number, the pei 'cent naphtha insoluble,the per cent chloroforir soluble, and the per cent soluble sludge. Thresults further show that with respect to thi: particular additive theaddition of 5% showec no material benefit over the addition of 3% tr themotor oil.

The table shows that when butyl ester of d butyl thio carbamic acid wasused-as the additive the copper-lead bearing loss was worse than wher noadditive was used, but in all other respect: the oil was markedlysuperior to the oil withoul the additive. The results on this particularadditive also demonstrate that in general the effectiveness of the 5%additive wasgreater than 3% 'From the foregoing it is apparent that wehavl discovered a new class of inhibitors for preventing deteriorationof motor oils when, used in internal combustion engines and forinhibitim bearing corrosion in such engines and that WI have discovereda new type of lubricant which i: unusually stable under operatingconditions i1 internal combustion engines and which gives eflicientoperation of the engine because of the smal amount of acid, sludge andvarnish formed.

We claim:

1. A lubricant for internal combustion engine: comprising a minerallubricating oil and a smal amount, sufilcient to inhibit oxidation ofsaid oi in use, of benzyl dibutyl dithio carbamate.

2. A lubricant in accordance with claim 1 ii which the amount of benzyldibutyl dithio car baimate is from 0.5 to 5 by weight of the minera o1WILLIAM B. ROSS; WILLIAM J. BACKOFF.- NORMAN D. WILLIAMS.

